1. Technical Field
The present invention relates to a vehicle seat, and, in particular, to a vehicle seat including a seat back and an airbag disposed in the seat back.
2. Related Art
Regarding vehicle seats of automobiles or the like, airbag systems are known that protect an occupant in a vehicle seat from an impact of a collision by deploying an airbag disposed in a seat back.
For example, Japanese Unexamined Patent Application Publication (JP-A) 10-273000 describes a vehicle seat including a seat back frame, an elastic support member extending across the seat back frame, a seat pad disposed on a front surface of the elastic support member, a support plate disposed behind the elastic support member and having a rigid structure, and an airbag in a deflated state disposed in a space between the elastic support member and the support plate.
With the vehicle seat, when an impact of a predetermined level or greater is detected, an inflator is activated to deploy the airbag between the elastic support member and the support plate. Thus, during a collision, the airbag elastically supports backward movement of an occupant from behind and restrains the occupant, and absorbs the impact energy by being depressurized and deflated.
JP-A 2010-52621 describes an airbag device including a first airbag and a second airbag. The first airbag is disposed in a lower back part of a seat back of a front seat and deploys toward an occupant in a rear seat. The second airbag, which is in a flat state, is disposed in a space in the seat back of the front seat, the space being on the front side of an elastic support member extending across a seat back frame.
Thus, when an impact of a predetermined level or greater is detected, an inflator is activated to deploy the first airbag toward an occupant in the rear seat. Therefore, even if the occupant in the rear seat is moved forward by an impact during a collision, the occupant is prevented from strongly colliding with the back surface of the front seat. Moreover, the second airbag deploys so as to elastically support backward movement of the upper body of an occupant in the front seat during a collision from behind and protects the occupant. The timings at which the first and second airbags are deployed are controlled so as to appropriately protect the occupants.
As described above, the vehicle seat described in JP-A 10-273000 protects an occupant in the vehicle seat by using an airbag and a support plate, which is disposed behind and outside of the airbag and which has a rigid structure. To be specific, the airbag alleviates an impact due to backward movement of the occupant, and the support plate first receives an impact exerted from behind the seat back and then the airbag absorbs the impact.
Accordingly, in a case where the vehicle seat is a front seat, if an occupant in a rear seat collides with the front seat from behind the seat back, a considerable impact is generated when the occupant collides with the support plate. Accordingly, an impact from behind might not be gently received, and therefore not only may the occupant in the rear seat receive considerable damage to a knee or the like but also the occupant in the front seat may receive a considerable impact.
On the other hand, the airbag device described in JP-A 2010-52621 can protect an occupant in a front seat and reduce damage to the occupant because the second airbag deploys in the seat back of the front seat. Moreover, the airbag device can protect an occupant in a rear seat because the first airbag deploys toward the occupant in the rear seat. However, it is necessary not only to provide the second airbag in the seat back but also to provide the first airbag, which deploys backward and outward from the seat back, in the lower part of the seat back of the front seat. Therefore, the structure of the seat back becomes complex, and it becomes difficult to control the airbags.
Moreover, because the first airbag deploys by a large amount in a direction diagonally upward from a lower back part of the seat back of the front seat toward an occupant in the rear seat, the deployment shape of the first airbag becomes unstable. Therefore, the airbag device might not be able to stably and reliably receive and absorb an impact extorted on the occupant in the rear seat when the occupant collides with the seat back of the front seat.
As described above, in each of the structures of the related art documents, there is room for improvement in directly protecting an occupant in the front seat and protecting the occupant from an impact exerted from behind the seat back by using an airbag and a simple structure.
Note that, in vehicles, such as automobiles, a collision of a knee or the like of an occupant in a rear seat with the seat back of a front seat may occur not only during a frontal collision but also during a rear-end collision in the following situation: a situation where a rear part of the vehicle body becomes deformed during a rear-end collision and an occupant in a rear seat is pushed forward due to the deformation and a knee of the occupant strongly collides with the back surface of the seat back of the front seat.